You can place a flamethrower on ANY car. Here is a CLEO script that checks to see if you are driving a vehicle and you can use the "+" key on the numpad to activate the flame.
{$VERSION 3.1.0027}
{$CLEO .cs}
//-------------MAIN---------------
thread 'FLAME_CAR'
//Checks to see if the player is defined and driving any vehicle (might need restrictions)
:FLAME_CAR_19
wait 0
if and
Actor.Driving($PLAYER_ACTOR)
Player.Defined($PLAYER_CHAR)
jf @FLAME_CAR_19
//Get the player's car as 0@ and add an invisible man with a flamethrower on it.
:FLAME_CAR_44
03C0: 0@ = actor $PLAYER_ACTOR car
Model.Load(#FLAME)
Model.Load(#MALE01)
038B: load_requested_models
0407: store_coords_to 1@ 2@ 3@ from_car 0@ with_offset 0.0 0.0 0.0
5@ = Actor.Create(CivMale, #MALE01, 0.0, 0.0, 0.0)
01B2: give_actor 5@ weapon 37 ammo 99999 // Load the weapon model before using this
01B9: set_actor 5@ armed_weapon_to 37
Actor.WeaponAccuracy(5@) = 100
//If you remove this line you will see the invisible man.
0337: set_actor 5@ visibility 0
Actor.SetImmunities(5@, 1, 1, 1, 1, 1)
//Set the current vehicle to FIRE PROOF
Car.SetImmunities(0@, 0, 1, 0, 0, 0)
02A9: set_actor 5@ immune_to_nonplayer 1
0619: enable_actor 5@ collision_detection 0
06A7: put_actor 5@ into_turret_on_car 0@ at_car_offset 0.0 2.0 0.0 position 2 shooting_angle 0.0 0.0 with_weapon 37
Model.Destroy(#FLAME)
Model.Destroy(#MALE01)
//Wait for a keypress of 107 "+" on the numpad or LMB Fire
:FLAME_CAR_239
wait 0
if
Actor.InCar($PLAYER_ACTOR, 0@)
jf @FLAME_CAR_357
if
not Actor.Dead(5@)
jf @FLAME_CAR_379
if or
00E1: player 0 pressed_key 17
0AB0: key_pressed 107
jf @FLAME_CAR_239
//Need to add some target control here so far just fires forwards.
017B: set_actor 5@ weapon 37 ammo_to 99999
0407: store_coords_to 1@ 2@ 3@ from_car 0@ with_offset 0.0 100.0 0.0
0668: AS_actor 5@ rotate_and_shoot_at 1@ 2@ 3@ 100 ms
jump @FLAME_CAR_239
//Player left car make it normal.
:FLAME_CAR_357
Actor.DestroyInstantly(5@)
Car.RemoveReferences(0@)
wait 1000
jump @FLAME_CAR_19
//Invisible man dead? REALLY! Wow, how did you manage that?
:FLAME_CAR_379
Actor.DestroyInstantly(5@)
Car.RemoveReferences(0@)
jump @FLAME_CAR_44
I don't know if this works with ALL vehicles somewhat untested. Have fun you funny arsonist you!
EDIT: I made some changes lowered my invisible man to make the flames seem to come from the grill. Added LMB keypress. I tested a BMX that is funny riding a BMX shooting flames. Also since you are not holding the weapon the cops don't blame you.